init formula calculation engine, ref #65 and #599

1 files changed, 46 insertions, 0 deletions

diff --git a/lib.go b/lib.go
index 83cdb4a..79c7cd4 100644
--- a/lib.go
+++ b/lib.go
@@ -12,6 +12,7 @@ package excelize
 import (
 	"archive/zip"
 	"bytes"
+	"container/list"
 	"fmt"
 	"io"
 	"log"
@@ -305,3 +306,48 @@ func genSheetPasswd(plaintext string) string {
 	password ^= 0xCE4B
 	return strings.ToUpper(strconv.FormatInt(password, 16))
 }
+
+// Stack defined an abstract data type that serves as a collection of elements.
+type Stack struct {
+	list *list.List
+}
+
+// NewStack create a new stack.
+func NewStack() *Stack {
+	list := list.New()
+	return &Stack{list}
+}
+
+// Push a value onto the top of the stack.
+func (stack *Stack) Push(value interface{}) {
+	stack.list.PushBack(value)
+}
+
+// Pop the top item of the stack and return it.
+func (stack *Stack) Pop() interface{} {
+	e := stack.list.Back()
+	if e != nil {
+		stack.list.Remove(e)
+		return e.Value
+	}
+	return nil
+}
+
+// Peek view the top item on the stack.
+func (stack *Stack) Peek() interface{} {
+	e := stack.list.Back()
+	if e != nil {
+		return e.Value
+	}
+	return nil
+}
+
+// Len return the number of items in the stack.
+func (stack *Stack) Len() int {
+	return stack.list.Len()
+}
+
+// Empty the stack.
+func (stack *Stack) Empty() bool {
+	return stack.list.Len() == 0
+}